U.S. patent number 9,188,770 [Application Number 14/213,371] was granted by the patent office on 2015-11-17 for zoom lens and image pickup apparatus equipped with same.
This patent grant is currently assigned to OLYMPUS CORPORATION. The grantee listed for this patent is OLYMPUS CORPORATION, OLYMPUS IMAGING CORP.. Invention is credited to Mayu Miki, Akinori Nishio, Tomoyuki Satori, Masahito Watanabe.
United States Patent |
9,188,770 |
Nishio , et al. |
November 17, 2015 |
Zoom lens and image pickup apparatus equipped with same
Abstract
A zoom lens consists of, in order from the object side, a first
lens unit having a positive refractive power, a second lens unit
having a negative refractive power, a third lens unit having a
positive refractive power, a fourth lens unit having a negative
refractive power, and a fifth lens unit having a positive
refractive power. The first lens unit and the second lens unit move
during zooming from the wide angle end to the telephoto end. The
zoom lens satisfies the following conditional expressions (1), (2),
and (3): f.sub.t/f.sub.w>6.0 (1), Fno.sub.(T)<3.5 (2),and
.SIGMA.d/f.sub.t<0.6 (3).
Inventors: |
Nishio; Akinori (Tokyo,
JP), Miki; Mayu (Tokyo, JP), Watanabe;
Masahito (Tokyo, JP), Satori; Tomoyuki (Kanagawa,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
OLYMPUS IMAGING CORP.
OLYMPUS CORPORATION |
Tokyo
Tokyo |
N/A
N/A |
JP
JP |
|
|
Assignee: |
OLYMPUS CORPORATION (Tokyo,
JP)
|
Family
ID: |
51526042 |
Appl.
No.: |
14/213,371 |
Filed: |
March 14, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20140268365 A1 |
Sep 18, 2014 |
|
Foreign Application Priority Data
|
|
|
|
|
Mar 14, 2013 [JP] |
|
|
2013-052199 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B
7/04 (20130101); G02B 15/145121 (20190801) |
Current International
Class: |
G02B
15/14 (20060101); G02B 15/173 (20060101); G02B
7/04 (20060101) |
Field of
Search: |
;359/683 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Choi; William
Attorney, Agent or Firm: Kenyon & Kenyon LLP
Claims
What is claimed is:
1. A zoom lens consisting of, in order from the object side: a
first lens unit having a positive refractive power; a second lens
unit having a negative refractive power; a third lens unit having a
positive refractive power; a fourth lens unit having a negative
refractive power; and a fifth lens unit having a positive
refractive power, wherein the first lens unit and the fifth lens
unit move during zooming from the wide angle end to the telephoto
end, and the following conditional expressions (1), (2), and (3)
are satisfied: f.sub.t/f.sub.w>6.0 (1), Fno.sub.(T)<3.5 (2),
and .SIGMA.d/f.sub.t<0.6 (3), where f.sub.t is the focal length
of the entire zoom lens system at the telephoto end, f.sub.w is the
focal length of the entire zoom lens system at the wide angle end,
Fno(.sub.T) is the F-number of the entire zoom lens system at the
telephoto end, and .SIGMA.d is the sum of the thicknesses of the
first to fifth lens units, where the thickness of each lens unit
refers to the distance on the optical axis from the lens surface
closest to the object side to the lens surface closest to the image
side in each lens unit.
2. A zoom lens according to claim 1, wherein the second lens unit
and the third lens unit move during zooming from the wide angle end
to the telephoto end, and the following conditional expression (4)
is satisfied: 2<.DELTA..sub.2G/|.DELTA..sub.3G|<5 (4) where
.DELTA..sub.2G is the amount of shift of the second lens unit with
zooming from the wide angle end to the telephoto end,
.DELTA..sub.3G is the amount of shift of the third lens unit with
zooming from the wide angle end to the telephoto end, where the
amounts of shift are calculated as the amounts of shift from the
positions of the respective lens units at the wide angle end, and
shifts toward the image plane are represented by positive
values.
3. A zoom lens according to claim 1, wherein the second lens unit
moves during zooming from the wide angle end to the telephoto end,
and the following conditional expression (5) is satisfied:
0.15.ltoreq..DELTA..sub.2G/L.sub.t.ltoreq.0.5 (5), where
.DELTA..sub.2G is the amount of shift of the second lens unit in
the zoom lens during zooming from the wide angle end to the
telephoto end, shifts toward the image plane being represented by
positive values, and L.sub.t is the overall length of the entire
zoom lens system at the telephoto end.
4. A zoom lens according to claim 1, wherein the third lens unit
moves during zooming from the wide angle end to the telephoto end,
and the following conditional expression (6) is satisfied:
0.05.ltoreq.|.DELTA..sub.3G|/L.sub.t.ltoreq.0.2 (6), where A.sub.3G
is the amount of shift of the third lens unit in the zoom lens
during zooming from the wide angle end to the telephoto end, shifts
toward the image plane being represented by positive values, and
L.sub.t is the overall length of the entire zoom lens system at the
telephoto end.
5. A zoom lens according to claim 1, wherein the following
conditional expression (7) is satisfied:
0.2<(.beta..sub.2T/.beta..sub.2w)/(f.sub.t/f.sub.w)<0.6 (7),
where .beta..sub.2T is the lateral magnification of the second lens
unit at the telephoto end of the focal length range of the zoom
lens, and .beta..sub.2w is the lateral magnification of the second
lens unit at the wide angle end of the focal length range of the
zoom lens.
6. A zoom lens according to claim 1, wherein the following
conditional expression (8) is satisfied:
0.1<(.beta..sub.3T/.beta..sub.3w)/(f.sub.t/f.sub.w)<0.3 (8),
where .beta..sub.3T is the lateral magnification of the third lens
unit at the telephoto end of the focal length range of the zoom
lens, and .beta..sub.3w is the lateral magnification of the third
lens unit at the wide angle end of the focal length range of the
zoom lens.
7. A zoom lens according to claim 1, wherein the following
conditional expression (9) is satisfied: 0.05<|f.sub.2
|/f.sub.t<0.2 (9), where f.sub.2 is the focal length of the
second lens unit.
8. A zoom lens according to claim 1, wherein the following
conditional expression (10) is satisfied:
0.05<f.sub.3/f.sub.t<0.3 (10), where f.sub.3 is the focal
length of the third lens unit.
9. A zoom lens according to claim 1, wherein the following
conditional expression (11) is satisfied:
0.1<f.sub.5/f.sub.t<0.8 (11), where f.sub.5 is the focal
length of the fifth lens unit.
10. A zoom lens according to claim 1, wherein the fourth lens unit
consists of one lens.
11. A zoom lens according to claim 1, wherein the fourth lens unit
moves during zooming.
12. An image pickup apparatus comprising: a zoom lens according to
claim 1; and an image pickup element disposed on the image side of
the zoom lens and having an image pickup element having an image
pickup surface that receives an image formed by zoom lens.
13. A zoom lens consisting of, in order from the object side: a
first lens unit having a positive refractive power; a second lens
unit having a negative refractive power; a third lens unit having a
positive refractive power; a fourth lens unit having a negative
refractive power; and a fifth lens unit having a positive
refractive power, wherein the second lens unit consists of three
lenses, the fifth lens unit consists of one lens, the first lens
unit moves during zooming from the wide angle end to the telephoto
end, and the following conditional expressions (1) , (2), and (3)
are satisfied, f.sub.tf.sub.w>6.0 (1), Fno.sub.(T)<3.5 (2),
and .SIGMA.d/f.sub.t<0.6 (3), where f.sub.t is the focal length
of the entire zoom lens system at the telephoto end, f.sub.w is the
focal length of the entire zoom lens system at the wide angle end,
Fno.sub.(T) is the F-number of the entire zoom lens system at the
telephoto end, and .SIGMA.d is the sum of the thicknesses of the
first to fifth lens units, where the thickness of each lens unit
refers to the distance on the optical axis from the lens surface
closest to the object side to the lens surface closest to the image
side in each lens unit.
Description
CROSS-REFERENCE TO RELATED APPLICATION
The present application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 2013-052199
filed on Mar. 14, 2013; the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a zoom lens and an image pickup
apparatus equipped with the same.
2. Description of the Related Art
In recent times, digital cameras that pick up an image of an object
using a solid state image pickup element such as a CCD or CMOS have
replaced film cameras and become the mainstream. Furthermore,
various categories of digital cameras ranging from popular-priced
compact type cameras to function-rich cameras for professionals
have been developed.
Users of popular-priced digital cameras wish to enjoy easy shooting
in various shooting situations anywhere at any time. For this
reason, such users tend to favor small size digital cameras,
especially slim digital cameras that can be conveniently carried in
a pocket of clothes or a bag. Therefore, a further reduction in the
size of the taking lens system is demanded.
On the other hand, there is a trend toward an increase in the
number of pixels of image pickup elements, and high optical
performance consistent with the increased numbers of pixels of
image pick up elements are demanded. Furthermore, while zoom lenses
having zoom ratios higher than 10 have been developed to widen the
variety of shooting and have become popular, a further increase in
the zoom ratio is expected.
Digital cameras capable of performing image processing for
extending the sensitivity range or dynamic range to enable shooting
in high-contrast situations have also been developed, enabling
shooting without limitations in situations.
In shooting in dark places, while contrast can be corrected
electronically to some extent, use of a large-diameter lens or a
fast lens allows shooting in darker places and will increase the
variety of scenes that can be shot.
Since fast, large-diameter lenses enable clear image shooting even
with small incident light quantities, they can provide increased
choice, such as higher shutter speeds in continuous shooting of a
moving object, to photographers. For this reason, large-diameter
lenses have been receiving attention in recent times.
As a prior art zoom lens having a relatively high zoom ratio and
high speed (or small F-number) throughout the entire focal length
range from the wide angle end to the telephoto end, a zoom lens
including, in order from the object side, a positive first lens
unit, a negative second lens unit, a positive third lens unit,
negative fourth lens unit, and a positive fifth lens unit have been
known (Japanese Patent Application Laid-Open No. 2008-304706).
SUMMARY OF THE INVENTION
A zoom lens according to a first aspect of the present invention
consists of, in order from the object side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power;
a third lens unit having a positive refractive power;
a fourth lens unit having a negative refractive power; and
a fifth lens unit having a positive refractive power, wherein
the first lens unit and the fifth lens unit move during zooming
from the wide angle end to the telephoto end, and
the following conditional expressions (1), (2), and (3) are
satisfied: ft/fw>6.0 (1), Fno(T)<3.5 (2),and
.SIGMA.d/ft<0.6 (3), where ft is the focal length of the entire
zoom lens system at the telephoto end, fw is the focal length of
the entire zoom lens system at the wide angle end, Fno(T) is the
F-number of the entire zoom lens system at the telephoto end, and
.SIGMA.d is the sum of the thicknesses of the first to fifth lens
units, where the thickness of each lens unit refers to the distance
on the optical axis from the lens surface closest to the object
side to the lens surface closest to the image side in each lens
unit.
A zoom lens according to a second aspect of the present invention
consists of, in order from the object side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power;
a third lens unit having a positive refractive power;
a fourth lens unit having a negative refractive power; and
a fifth lens unit having a positive refractive power, wherein
the second lens unit consists of three lenses,
the fifth lens unit consists of one lens,
the first lens unit moves during zooming from the wide angle end to
the telephoto end, and
the following conditional expressions (1), (2), and (3) are
satisfied, ft/fw>6.0 (1), Fno(T)<3.5 (2),and
.SIGMA.d/ft<0.6 (3), where ft is the focal length of the entire
zoom lens system at the telephoto end, fw is the focal length of
the entire zoom lens system at the wide angle end, Fno(T) is the
F-number of the entire zoom lens system at the telephoto end, and
.SIGMA.d is the sum of the thicknesses of the first to fifth lens
units, where the thickness of each lens unit refers to the distance
on the optical axis from the lens surface closest to the object
side to the lens surface closest to the image side in each lens
unit.
An image pickup apparatus according to the present invention
comprises a zoom lens according to any one of the above-described
aspects of the present invention and an image pickup element
disposed on the image side of the zoom lens and having an image
pickup surface that receives an image formed by the zoom lens.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A, 1B, and 1C are cross sectional views of a zoom lens
according to a first example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
1A shows the state at the wide angle end, FIG. 1B shows the state
in an intermediate focal length state, and FIG. 1C shows the state
at the telephoto end;
FIGS. 2A, 2B, and 2C are cross sectional views of a zoom lens
according to a second example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
2A shows the state at the wide angle end, FIG. 2B shows the state
in an intermediate focal length state, and FIG. 2C shows the state
at the telephoto end;
FIGS. 3A, 3B, and 3C are cross sectional views of a zoom lens
according to a third example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
3A shows the state at the wide angle end, FIG. 3B shows the state
in an intermediate focal length state, and FIG. 3C shows the state
at the telephoto end;
FIGS. 4A, 4B, and 4C are cross sectional views of a zoom lens
according to a fourth example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
4A shows the state at the wide angle end, FIG. 4B shows the state
in an intermediate focal length state, and FIG. 4C shows the state
at the telephoto end;
FIGS. 5A, 5B, and 5C are cross sectional views of a zoom lens
according to a fifth example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
5A shows the state at the wide angle end, FIG. 5B shows the state
in an intermediate focal length state, and FIG. 5C shows the state
at the telephoto end;
FIGS. 6A to 6L are aberration diagrams of the zoom lens according
to the first embodiment in the state in which the zoom lens is
focused on an object point at infinity;
FIGS. 7A to 7L are aberration diagrams of the zoom lens according
to the second embodiment in the state in which the zoom lens is
focused on an object point at infinity;
FIGS. 8A to 8L are aberration diagrams of the zoom lens according
to the third embodiment in the state in which the zoom lens is
focused on an object point at infinity;
FIGS. 9A to 9L are aberration diagrams of the zoom lens according
to the fourth embodiment in the state in which the zoom lens is
focused on an object point at infinity;
FIGS. 10A to 10L are aberration diagrams of the zoom lens according
to the fifth embodiment in the state in which the zoom lens is
focused on an object point at infinity;
FIG. 11 is a cross-sectional view of a compact camera as an image
pickup apparatus using small CCD or CMOS as an image pickup
element, in which the zoom lens according to the present invention
is incorporated;
FIG. 12 is a front perspective view showing an appearance of a
digital camera as an image pickup apparatus;
FIG. 13 is a rear perspective view showing an appearance of the
digital camera; and
FIG. 14 is a block diagram showing an internal circuit of main
components of the digital camera.
DETAILED DESCRIPTION OF THE INVENTION
In the following, embodiments and examples of the zoom lens and the
image pickup apparatus equipped with the same according to the
present invention will be described in detail with reference to the
drawings. It should be understood, however, that the present
invention is by no means limited by the embodiments and
examples.
Operations and advantages of the zoom lens according to embodiments
will be described prior to the description of examples.
A zoom lens according to an embodiment of the present invention is
composed of, in order from the object side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power;
a third lens unit having a positive refractive power;
a fourth lens unit having a negative refractive power; and
a fifth lens unit having a positive refractive power, wherein
the first lens unit and the fifth lens unit move during zooming
from the wide angle end to the telephoto end, and
the following conditional expressions (1), (2), and (3) are
satisfied: f.sub.t/f.sub.w>6.0 (1), Fno.sub.(T)<3.5 (2),and
.SIGMA.d/f.sub.t<0.6 (3), where f.sub.t is the focal length of
the entire zoom lens system at the telephoto end, f.sub.w is the
focal length of the entire zoom lens system at the wide angle end,
Fno.sub.(T) is the F-number of the entire zoom lens system at the
telephoto end, and .SIGMA.d is the sum of the thicknesses of the
first to fifth lens units, where the thickness of each lens unit
refers to the distance on the optical axis from the lens surface
closest to the object side to the lens surface closest to the image
side in each lens unit.
The zoom lens according to this embodiment includes, in order from
the object side, a first lens unit having a positive refractive
power, a second lens unit having a negative refractive power, a
third lens unit having a positive refractive power, a fourth lens
unit having a negative refractive power, and a fifth lens unit
having a positive refractive power. In this zoom lens, the first
lens unit and the fifth lens unit move during zooming from the wide
angle end to the telephoto end of the focal length range.
With the above-described configuration, the lens units are adapted
to efficiently contribute to the variation of magnification in
cooperation, whereby the variation of aberrations with zooming can
be kept small, and the zoom lens can have a high zoom ratio as an
optical system while being small in the overall length with the
amount of shift of each lens unit being not so large.
Conditional expression (1) is a condition relating to the zoom
ratio of the zoom lens. If conditional expression (1) is satisfied,
the zoom lens can have a high zoom ratio.
Conditional expression (2) is a condition relating to the F-number
of the zoom lens at the telephoto end of the focal length range. If
the conditional expression (2) is satisfied, the zoom lens can have
appropriately high speed at the telephoto end.
Conditional expression (3) is a condition relating to the sum of
the thicknesses of the first to fifth lens units. Conditional
expression (3) limits the value of the sum of the thicknesses
normalized by the focal length at the telephoto end. Here, the
thickness of each lens unit refers to the distance on the optical
axis from the lens surface closest to the object side to the lens
surface closest to the image side in each lens unit. Satisfying
conditional expression (3) makes the overall length of the zoom
lens small.
If the value of .SIGMA.d/f.sub.t in conditional expression (3)
exceeds the upper limit, the sum of the thicknesses of the first to
fifth lens units is so large and the overall length of the zoom
lens is so large accordingly that it is difficult to house the zoom
lens in a collapsed state. In other words, it is difficult to make
the overall length of the zoom lens small.
A zoom lens according to another aspect of the embodiment is
composed of, in order from the object side,
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power;
a third lens unit having a positive refractive power;
a fourth lens unit having a negative refractive power; and
a fifth lens unit having a positive refractive power, wherein
the second lens unit is composed of three lenses,
the fifth lens unit is composed of one lens,
the first lens unit moves during zooming from the wide angle end to
the telephoto end, and
the following conditional expressions (1), (2), and (3) are
satisfied, f.sub.t/f.sub.w>6.0 (1), Fno.sub.(T)<3.5 (2),and
.SIGMA.d/f.sub.t<0.6 (3), where f.sub.t is the focal length of
the entire zoom lens system at the telephoto end, f.sub.w is the
focal length of the entire zoom lens system at the wide angle end,
Fno.sub.(T) is the F-number of the entire zoom lens system at the
telephoto end, and .SIGMA.d is the sum of the thicknesses of the
first to fifth lens units, where the thickness of each lens unit
refers to the distance on the optical axis from the lens surface
closest to the object side to the lens surface closest to the image
side in each lens unit.
The zoom lens according to this embodiment includes, in order from
the object side, a first lens unit having a positive refractive
power, a second lens unit having a negative refractive power, a
third lens unit having a positive refractive power, a fourth lens
unit having a negative refractive power, and a fifth lens unit
having a positive refractive power. In this zoom lens, the second
lens unit is composed of three lenses, the fifth lens unit is
composed of one lens, and the first lens unit moves toward the
object side during zooming from the wide angle end to the telephoto
end.
With the above-described configuration, the lens units are adapted
to efficiently contribute to the variation of magnification in
cooperation, whereby the variation of aberrations with zooming can
be kept small, and the optical system can have a high zoom ratio
while being small in the overall length with the amount of shift of
each lens units being not so large.
Moreover, since the second and fifth lens units are composed of a
minimized number of lenses, the thickness of these lens units can
be small. Thus, the optical system can be compact.
In the zoom lens according to the embodiment, it is preferred that
the second lens unit and the third lens unit move during zooming
from the wide angle end to the telephoto end, and the following
conditional expression (4) be satisfied:
2<.DELTA..sub.2G/|.DELTA..sub.3G|<5 (4), where .DELTA..sub.2G
is the amount of shift of the second lens unit with zooming from
the wide angle end to the telephoto end, .DELTA..sub.3G is the
amount of shift of the third lens unit with zooming from the wide
angle end to the telephoto end, where the amounts of shift are
calculated as the amounts of shift from the positions of the
respective lens units at the wide angle end, and shifts toward the
image plane are represented by positive values.
Conditional expression (4) specifies a condition relating to the
ratio of the amount of shift of the second lens unit and the amount
of shift of the third lens unit. If the value of
.DELTA..sub.2G/|.DELTA..sub.3G| in conditional expression (4) falls
below the lower limit, the amount of shift of the third lens unit
with zooming is so large that it is difficult to make the overall
length of the zoom lens appropriately small.
Furthermore, when the amount of shift of the third lens unit with
zooming is large, a large stop diameter is necessitated when the
zoom lens is to be designed to have appropriately high speed at the
telephoto end, leading to a large lens diameter in the third lens
unit.
Still further, when the lens diameter of the third lens unit is
large, the lens thickness also needs to be large. Therefore, it is
difficult to make the zoom lens compact.
Still further, when the lens diameter of the third lens unit is
large, the volume and the weight of the third lens unit would also
be large. Therefore, in the case where the third lens unit serves
as a lens unit that is driven for image stabilization, a strong
external force for driving the third lens unit is required. This is
not desirable.
On the other hand, if the value of .DELTA..sub.2G/|.DELTA..sub.3G|
in conditional expression (4) exceeds the upper limit, the amount
of shift of the second lens unit with zooming is so large that the
overall length of the zoom lens cannot be made small.
In the zoom lens according to the embodiment, it is preferred that
the second lens unit move during zooming from the wide angle end to
the telephoto end, and the following conditional expression (5) be
satisfied: 0.15.ltoreq..DELTA..sub.2G/L.sub.t.ltoreq.0.5 (5), where
.DELTA..sub.2G is the amount of shift of the second lens unit in
the zoom lens during zooming from the wide angle end to the
telephoto end, shifts toward the image plane being represented by
positive values, and L.sub.t is the overall length of the entire
zoom lens system at the telephoto end.
Conditional expression (5) is a condition relating to the amount of
shift of the second lens unit. Conditional expression (5) limits
the value of the amount of shift of the second lens unit normalized
by the overall length of the entire zoom lens system at the
telephoto end.
If the value of .DELTA..sub.2G/L.sub.t in conditional expression
(5) falls below the lower limit, the amount of shift of the second
lens unit with zooming is so small that it is difficult to achieve
an appropriately high zoom ratio.
On the other hand, if the value of .DELTA..sub.2G/L.sub.t in
conditional expression (5) exceeds the upper limit, the amount of
shift of the second lens unit with zooming is so large that it is
difficult to make the overall length of the zoom lens small.
In the zoom lens according to the embodiment, it is preferred that
the third lens unit move during zooming from the wide angle end to
the telephoto end, and the following conditional expression (6) be
satisfied: 0.05.ltoreq.|.DELTA..sub.3G|/L.sub.t.ltoreq.0.2 (6),
where .DELTA..sub.3G is the amount of shift of the third lens unit
in the zoom lens during zooming from the wide angle end to the
telephoto end, shifts toward the image plane being represented by
positive values, and L.sub.t is the overall length of the entire
zoom lens system at the telephoto end.
Conditional expression (6) is a condition relating to the amount of
shift of the third lens unit. Conditional expression (6) limits the
value of the amount of shift of the third lens unit normalized by
the overall length of the entire zoom lens system at the telephoto
end.
If the value of .DELTA..sub.3G/L.sub.t in conditional expression
(6) falls below the lower limit, the amount of shift of the third
lens unit with zooming is so small that it is difficult to achieve
an appropriately high zoom ratio.
If the value of .DELTA..sub.3G/L.sub.t in conditional expression
(6) exceeds the upper limit, the amount of shift of the third lens
unit with zooming is so large that it is difficult to make the
overall length of the zoom lens appropriately small. Furthermore,
when the amount of shift of the third lens unit with zooming is
large, a large stop diameter is necessitated when the zoom lens is
to be designed to have appropriately high speed at the telephoto
end, leading to a large lens diameter in the third lens unit.
Still further, when the lens diameter of the third lens unit is
large, the lens thickness also needs to be large. Therefore, it is
difficult to make the zoom lens compact.
Still further, when the lens diameter of the third lens unit is
large, the volume and the weight of the third lens unit would also
be large. Therefore, in the case where the third lens unit serves
as a lens unit that is driven for image stabilization, a strong
external force for driving the third lens unit is required. This is
not desirable.
In the zoom lens according to the embodiment, it is preferred that
the following conditional expression (7) be satisfied:
0.2<(.beta..sub.2T/.beta..sub.2W)/(f.sub.t/f.sub.w)<0.6 (7),
where .beta..sub.2T is the lateral magnification of the second lens
unit at the telephoto end of the focal length range of the zoom
lens, and .beta..sub.2W is the lateral magnification of the second
lens unit at the wide angle end of the focal length range of the
zoom lens.
Conditional expression (7) is a condition relating to the
proportion of the contribution of the second lens unit to the
magnification variation, among the lens units contributing to the
magnification variation.
If the value of (.beta..sub.2T/.beta..sub.2W)/(f.sub.t/f.sub.w) in
conditional expression (7) falls below the lower limit, the
contribution of the second lens unit to the magnification variation
is so small that the other lens units need to be designed to
provide large contributions to the magnification variation,
undesirably leading to increased spherical aberration and coma.
If the value of (.beta..sub.2T/.beta..sub.2W)/(f.sub.t/f.sub.w) in
conditional expression (7) exceeds the upper limit, curvature of
field and chromatic aberration of magnification in the focal length
range near the wide angle end will increase undesirably.
In the zoom lens according to the embodiment, it is preferred that
the following conditional expression (8) be satisfied:
0.1<(.beta..sub.3T/.beta..sub.3W)/(f.sub.t/f.sub.w)<0.3 (8),
where .beta..sub.3T is the lateral magnification of the third lens
unit at the telephoto end of the focal length range of the zoom
lens, and .beta..sub.3W is the lateral magnification of the third
lens unit at the wide angle end of the focal length range of the
zoom lens.
Conditional expression (8) is a condition relating to the
proportion of the contribution of the third lens unit to the
magnification variation, among the lens units contributing to the
magnification variation.
If the value of (.beta..sub.3T/.beta..sub.3W)/(f.sub.t/f.sub.w) in
conditional expression (8) falls below the lower limit, the
contribution of the third lens unit to the magnification variation
is so small that the other lens units need to be designed to
provide large contributions to the magnification variation,
undesirably leading to increased curvature of field and chromatic
aberration of magnification.
If the value of (.beta..sub.3T/.beta..sub.3W)/(f.sub.t/f.sub.w) in
conditional expression (8) exceeds the upper limit, spherical
aberration and coma will increase undesirably.
In the zoom lens according to the embodiment, it is preferred that
the following conditional expression (9) be satisfied:
0.05<|f.sub.2|/f.sub.t<0.2 (9), where f.sub.2 is the focal
length of the second lens unit.
Conditional expression (9) specifies an appropriate range for the
value of the ratio of the focal length of the second lens unit and
the focal length of the entire zoom lens system at the telephoto
end.
If the value of |f.sub.2|/f.sub.t in conditional expression (9)
exceeds the upper limit, the refractive power of the second lens
unit is low, leading to a large overall length of the zoom lens.
Therefore, it is difficult to make the zoom lens compact.
If the value of |f.sub.2|/f.sub.t in conditional expression (9)
falls below the lower limit, the refractive power of the second
lens unit is unduly high, and the balance of the Petzval sum is
deteriorated in the focal length range near the wide angle end.
Then, it is not possible to keep the image plane flat, resulting in
large curvature of field. Furthermore, unduly high refractive power
of the second lens unit causes large chromatic aberration of
magnification in the focal length range near the wide angle end,
leading to deterioration of the performance.
In the zoom lens according to the present invention, it is
preferred that the following conditional expression (10) be
satisfied: 0.05<f.sub.3/f.sub.t<0.3 (10), where f.sub.3 is
the focal length of the third lens unit.
Conditional expression (10) specifies an appropriate range for the
value of the ratio of the focal length of the third lens unit and
the focal length of the entire zoom lens system at the telephoto
end.
If the value of |f.sub.3|/f.sub.t in conditional expression (10)
exceeds the upper limit, the refractive power of the third lens
unit is low, leading to a large overall length of the zoom lens.
Therefore, it is difficult to make the zoom lens compact.
If the value of |f.sub.3|/f.sub.t in conditional expression (10)
falls below the lower limit, the refractive power of the third lens
unit is unduly high, and large spherical aberration and coma are
generated. If the number of lenses is increased to reduce the
aberrations, the thickness of the third lens unit necessarily
increases. Then, it is difficult to make the zoom lens compact.
In the zoom lens according to the embodiment, it is preferred that
the following conditional expression (11) be satisfied:
0.1<f.sub.5/f.sub.t<0.8 (11), where f.sub.5 is the focal
length of the fifth lens unit.
Conditional expression (11) specifies an appropriate range for the
value of the ratio of the focal length of the fifth lens unit and
the focal length of the entire zoom lens system at the telephoto
end.
If the value of |f.sub.5|/f.sub.t in conditional expression (11)
exceeds the upper limit, the refractive power of the fifth lens
unit is low, leading to a large overall length of the zoom lens.
Therefore, it is difficult to make the zoom lens compact.
If the value of |f.sub.5|/f.sub.t in conditional expression (11)
falls below the lower limit, large curvature of field and chromatic
aberration of magnification are generated.
In the zoom lens according to the embodiment, it is preferred that
the fourth lens unit be composed of one lens.
If the fourth lens unit is composed of one lens, the constitution
of the fourth lens unit is minimized, and the thickness of the
fourth lens unit is kept small. Therefore, the optical system can
be made compact.
In the zoom lens according to the embodiment, it is preferred that
the fourth lens unit move during zooming.
If the fourth lens unit is moved during zooming, the fourth lens
unit can efficiently contribute to correction of aberrations such
as curvature of field and spherical aberration and to the
magnification variation. In consequence, contributions to the
magnification variation are efficiently shared among the lens
units. Therefore, it is possible to provide an optical system that
has a high zoom ratio with small variation in aberrations during
zooming while keeping the amounts of shift of the lens units small
to make the optical system compact.
An image pickup apparatus according to an embodiment includes a
zoom lens according to any one of the above-described aspect and an
image pickup element disposed on the image side of the zoom lens
and having an image pickup surface that receives an image formed by
the zoom lens.
With this configuration, contributions to the magnification
variation are efficiently shared among the lens units. Therefore it
is possible to provide an image pickup apparatus including an
optical system that has a high zoom ratio with small variation in
aberrations during zooming while keeping the amounts of shift of
the lens units small to make the optical system compact.
It is preferred that two or more of the above-described features be
adopted in combination.
It is more preferred that the upper and/or lower limit values in
the conditional expressions presented in the foregoing be further
limited as follows in order that the advantages can be enjoyed more
surely.
In conditional expression (1), it is more preferred that the lower
limit value be 8.0.
In conditional expression (2), it is more preferred that the upper
limit value be 3.0.
In conditional expression (3), it is more preferred that the upper
limit value be 0.5.
In conditional expression (4), it is more preferred that the upper
limit value be 3, and the lower limit value be 2.1.
In conditional expression (5), it is more preferred that the upper
limit value be 0.4, and the lower limit value be 0.18.
In conditional expression (6), it is more preferred that the upper
limit value be 0.15, and the lower limit value be 0.07.
In conditional expression (7), it is more preferred that the upper
limit value be 0.5, and the lower limit value be 0.25.
In conditional expression (8), it is more preferred that the upper
limit value be 0.25, and the lower limit value be 0.11.
In conditional expression (9), it is more preferred that the upper
limit value be 0.18, and the lower limit value be 0.1.
In conditional expression (10), it is more preferred that the upper
limit value be 0.25, and the lower limit value be 0.1.
In conditional expression (11), it is more preferred that the upper
limit value be 0.6, and the lower limit value be 0.2.
Embodiments from a first embodiment to a fifth embodiment of the
zoom lens will be described below.
FIGS. 1A, 1B, and 1C are cross sectional views of a zoom lens
according to a first example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
1A shows the state at the wide angle end, FIG. 1B shows the state
in an intermediate focal length state, and FIG. 1C shows the state
at the telephoto end;
FIGS. 2A, 2B, and 2C are cross sectional views of a zoom lens
according to a second example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
2A shows the state at the wide angle end, FIG. 2B shows the state
in an intermediate focal length state, and FIG. 2C shows the state
at the telephoto end;
FIGS. 3A, 3B, and 3C are cross sectional views of a zoom lens
according to a third example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
3A shows the state at the wide angle end, FIG. 3B shows the state
in an intermediate focal length state, and FIG. 3C shows the state
at the telephoto end;
FIGS. 4A, 4B, and 4C are cross sectional views of a zoom lens
according to a fourth example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
4A shows the state at the wide angle end, FIG. 4B shows the state
in an intermediate focal length state, and FIG. 4C shows the state
at the telephoto end; and
FIGS. 5A, 5B, and 5C are cross sectional views of a zoom lens
according to a fifth example of the present invention taken along
its optical axis, showing its configuration in the state in which
the zoom lens is focused on an object point at infinity, where FIG.
5A shows the state at the wide angle end, FIG. 5B shows the state
in an intermediate focal length state, and FIG. 5C shows the state
at the telephoto end.
In FIGS. 1A to 5C, a first lens unit is denoted by G1, a second
lens unit is denoted by G2, a third lens unit is denoted by G3, a
fourth lens unit is denoted by G4, a fifth lens unit is denoted by
G5, an aperture stop is denoted by S, a plane parallel plate
constituting a low pass filter on which wavelength restriction
coating for blocking or reducing infrared light is applied is
denoted by F, a plane parallel plate constituting a cover glass for
an electronic image pickup element is denoted by C, and the image
plane is denoted by I. A multi-layer coating for wavelength
restriction may be applied to the surface of the cover glass C. The
cover glass C may be adapted to have a low pass filtering function.
The low pass filtering effect of the plane parallel plate F may be
eliminated.
In all the examples, the aperture stop S moves integrally with the
third lens unit G3. All the numerical data of the examples given
below is for the state in which the zoom lens is focused on an
object at infinity. In the numerical data, dimensions are in
millimeters and angles are in degrees. Zoom data will be given for
the wide angle end (wide angle), for the intermediate focal length
state (intermediate), and for the telephoto end (telephoto).
It is preferred that focusing for focus adjustment be performed by
moving the fifth lens unit G5 or the fourth lens unit G4. Since the
fifth lens unit G5 and the fourth lens unit G4 are light in weight,
the load on the motor for driving the fifth lens unit G5 or the
fourth lens unit G4 for focusing is small. Focusing may be
performed by moving a lens unit other than the fifth lens unit G5
or the fourth lens unit G4. A plurality of lens units may be moved
for focusing. Focusing may be performed by advancing the entirety
of the lens system, or by moving one or some of the lenses forward
and backward.
When a lens unit is to be shifted for image stabilization, it is
preferred that the lens unit to be shifted be the third lens unit
G3.
As shown in FIGS. 1A, 1B, and 1C, the zoom lens according to the
first example includes, in order from the object side, a first lens
unit G1 having a positive refractive power, a second lens unit G2
having a negative refractive power, an aperture stop S, a third
lens unit G3 having a positive refractive power, a fourth lens unit
G4 having a negative refractive power, and a fifth lens unit G5
having a positive refractive power.
During zooming from the wide angle end to the telephoto end, the
first lens unit G1 moves toward the object side, the second lens
unit G2 moves toward the image side, the third lens unit G3 moves
toward the object side, the fourth lens unit G4 moves first toward
the image side and thereafter toward the object side, and the fifth
lens unit G5 moves toward the image side. The aperture stop S moves
integrally with the third lens unit G3.
The first lens unit G1 is composed of a cemented lens made up of a
negative meniscus lens L1 having a convex surface directed toward
the object side and a biconvex positive lens L2, and a positive
meniscus lens L3 having a convex surface directed toward the object
side. The second lens unit G2 is composed of a biconcave negative
lens L4, a biconcave negative lens L5, and a biconvex positive lens
L6. The third lens unit G3 is composed of a biconvex positive lens
L7, a cemented lens made up of a positive meniscus lens L8 having a
convex surface directed toward the object side and a negative
meniscus lens L9 having a convex surface directed toward the object
side, and a biconvex positive lens L10. The fourth lens unit G4 is
composed of a negative meniscus lens L11 having a convex surface
directed toward the object side. The fifth lens unit G5 is composed
of a biconvex positive lens L12. The lens elements in each lens
unit are arranged in the mentioned order from the object side.
There are nine aspheric surfaces, which include both surfaces of
the biconcave negative lens L5, both surfaces of the biconvex
positive lens L7, the image side surface of the biconvex positive
lens L10, both surfaces of the negative meniscus lens L11, and both
surfaces of the biconvex positive lens L12.
As shown in FIGS. 2A, 2B, and 2C, the zoom lens according to the
second example includes, in order from the object side, a first
lens unit G1 having a positive refractive power, a second lens unit
G2 having a negative refractive power, an aperture stop S, a third
lens unit G3 having a positive refractive power, a fourth lens unit
G4 having a negative refractive power, and a fifth lens unit G5
having a positive refractive power.
During zooming from the wide angle end to the telephoto end, the
first lens unit G1 moves toward the object side, the second lens
unit G2 moves toward the image side, the third lens unit G3 moves
toward the object side, the fourth lens unit G4 moves first toward
the image side and thereafter toward the object side, and the fifth
lens unit G5 moves toward the image side. The aperture stop S moves
integrally with the third lens unit G3.
The first lens unit G1 is composed of a cemented lens made up of a
negative meniscus lens L1 having a convex surface directed toward
the object side and a biconvex positive lens L2, and a positive
meniscus lens L3 having a convex surface directed toward the object
side. The second lens unit G2 is composed of a negative meniscus
lens L4 having a convex surface directed toward the object side, a
biconcave negative lens L5, and a biconvex positive lens L6. The
third lens unit G3 is composed of a biconvex positive lens L7, a
cemented lens made up of a positive meniscus lens L8 having a
convex surface directed toward the object side and a negative
meniscus lens L9 having a convex surface directed toward the object
side, and a biconvex positive lens L10. The fourth lens unit G4 is
composed of a biconcave negative lens L11. The fifth lens unit G5
is composed of a biconvex positive lens L12. The lens elements in
each lens unit are arranged in the mentioned order from the object
side.
There are five aspheric surfaces, which include the object side
surface of the biconvex positive lens L6, both surfaces of the
biconvex positive lens L7, the image side surface of the biconcave
negative lens L11, and the image side surface of the biconvex
positive lens L12.
As shown in FIGS. 3A, 3B, and 3C, the zoom lens according to the
third example includes, in order from the object side, a first lens
unit G1 having a positive refractive power, a second lens unit G2
having a negative refractive power, an aperture stop S, a third
lens unit G3 having a positive refractive power, a fourth lens unit
G4 having a negative refractive power, and a fifth lens unit G5
having a positive refractive power.
During zooming from the wide angle end to the telephoto end, the
first lens unit G1 moves first toward the image side and thereafter
toward the object side, the second lens unit G2 moves toward the
image side, the third lens unit G3 moves toward the object side,
the fourth lens unit G4 moves toward the object side, and the fifth
lens unit G5 moves toward the image side. The aperture stop S moves
integrally with the third lens unit G3.
The first lens unit G1 is composed of a cemented lens made up of a
negative meniscus lens L1 having a convex surface directed toward
the object side and a biconvex positive lens L2, and a positive
meniscus lens L3 having a convex surface directed toward the object
side. The second lens unit G2 is composed of a biconcave negative
lens L4, a biconcave negative lens L5, and a biconvex positive lens
L6. The third lens unit G3 is composed of a biconvex positive lens
L7, a cemented lens made up of a positive meniscus lens L8 having a
convex surface directed toward the object side and a negative
meniscus lens L9 having a convex surface directed toward the object
side, and a biconvex positive lens L10. The fourth lens unit G4 is
composed of a negative meniscus lens L11 having a convex surface
directed toward the object side. The fifth lens unit G5 is composed
of a biconvex positive lens L12. The lens elements in each lens
unit are arranged in the mentioned order from the object side.
There are four aspheric surfaces, which include the image side
surface of the biconcave negative lens L5, both surfaces of the
biconvex positive lens L7, and the image side surface of the
biconvex positive lens L12.
As shown in FIGS. 4A, 4B, and 4C, the zoom lens according to the
fourth example includes, in order from the object side, a first
lens unit G1 having a positive refractive power, a second lens unit
G2 having a negative refractive power, an aperture stop S, a third
lens unit G3 having a positive refractive power, a fourth lens unit
G4 having a negative refractive power, and a fifth lens unit G5
having a positive refractive power.
During zooming from the wide angle end to the telephoto end, the
first lens unit G1 moves first toward the image side and thereafter
toward the object side, the second lens unit G2 moves toward the
image side, the third lens unit G3 moves toward the object side,
the fourth lens unit G4 moves toward the object side, and the fifth
lens unit G5 moves toward the image side. The aperture stop S moves
integrally with the third lens unit G3.
The first lens unit G1 is composed of a cemented lens made up of a
negative meniscus lens L1 having a convex surface directed toward
the object side and a biconvex positive lens L2. The second lens
unit G2 is composed of a negative meniscus lens L3 having a convex
surface directed toward the object side, a biconcave negative lens
L4, and a positive meniscus lens L5 having a convex surface
directed toward the object side. The third lens unit G3 is composed
of a biconvex positive lens L6, a cemented lens made up of a
positive meniscus lens L7 having a convex surface directed toward
the object side and a negative meniscus lens L8 having a convex
surface directed toward the object side, and a biconvex positive
lens L9. The fourth lens unit G4 is composed of a biconcave
negative lens L10. The fifth lens unit G5 is composed of a biconvex
positive lens L11. The lens elements in each lens unit are arranged
in the mentioned order from the object side.
There are six aspheric surfaces, which include the image side
surface of the biconvex positive lens L2, the object side surface
of a biconcave negative lens L4, both surfaces of the biconvex
positive lens L6, and both surfaces of the biconvex positive lens
L11.
As shown in FIGS. 5A, 5B, and 5C, the zoom lens according to the
fifth example includes, in order from the object side, a first lens
unit G1 having a positive refractive power, a second lens unit G2
having a negative refractive power, an aperture stop S, a third
lens unit G3 having a positive refractive power, a fourth lens unit
G4 having a negative refractive power, and a fifth lens unit G5
having a positive refractive power.
During zooming from the wide angle end to the telephoto end, the
first lens unit G1 moves toward the object side, the second lens
unit G2 moves toward the image side, the third lens unit G3 moves
toward the object side, the fourth lens unit G4 moves first toward
the image side and thereafter toward the object side, and the fifth
lens unit G5 moves toward the image side. The aperture stop S moves
integrally with the third lens unit G3.
The first lens unit G1 is composed of a cemented lens made up of a
negative meniscus lens L1 having a convex surface directed toward
the object side and a biconvex positive lens L2, and a positive
meniscus lens L3 having a convex surface directed toward the object
side. The second lens unit G2 is composed of a negative meniscus
lens L4 having a convex surface directed toward the object side, a
biconcave negative lens L5, and a biconvex positive lens L6. The
third lens unit G3 is composed of a biconvex positive lens L7, a
negative meniscus lens L8 having a convex surface directed toward
the object side, and a biconvex positive lens L9. The fourth lens
unit G4 is composed of a negative meniscus lens L10 having a convex
surface directed toward the object side. The fifth lens unit G5 is
composed of a biconvex positive lens L11. The lens elements in each
lens unit are arranged in the mentioned order from the object
side.
There are five aspheric surfaces, which include the object side
surface of the biconvex positive lens L6, both surfaces of the
biconvex positive lens L7, the image side surface of the negative
meniscus lens L10, and the image side surface of the biconvex
positive lens L11.
Numerical data of each embodiment described above is shown below.
Apart from symbols described above, fb denotes a back focus, f1,
f2, . . . denotes a focal length of each lens unit, Fno denotes an
F number, .omega. denotes a half image angle, WE denotes a wide
angle end, ST denotes an intermediate state, TE denotes a telephoto
end, r denotes radius of curvature of each lens surface, d denotes
a distance between two lenses, nd denotes a refractive index of
each lens for a d-line, and vd denotes an Abbe's number for each
lens. The overall length of the lens system which will be described
later is a length which is obtained by adding the back focus to a
distance from the first lens surface up to the last lens surface.
fb (back focus) is a unit which is expressed upon air conversion of
a distance from the last lens surface up to a paraxial image
plane.
A shape of the aspheric surface is described by the following
expression (I) using each aspherical surface coefficient in each
embodiment, when Z is let to be a coordinate point on an optical
axis, and Y is let to be a coordinate point on a direction
orthogonal to the optical axis,
Z=(Y.sup.2/r)/[1+{1-(K+1)(Y/r).sup.2}.sup.1/2]+A.sub.4Y.sup.4+A.sub.6Y.su-
p.6+A.sub.8Y.sup.8+A.sub.10Y.sup.10 (I) where, r denotes a paraxial
radius of curvature, K denotes a conical coefficient, A.sub.4,
A.sub.6, A.sub.8, and A.sub.10 denote aspherical surface
coefficients of a fourth order, a sixth order, an eight order, a
tenth order, and a twelfth order respectively. Moreover, in the
aspherical surface coefficients, `e-n` (where, n is an integral
number) indicates `10.sup.-n`.
Example 1
TABLE-US-00001 Unit mm Surface data Surface no. r d nd .nu.d 1
46.380 1.10 1.84666 23.78 2 34.460 4.50 1.49700 81.54 3 -733.704
0.18 4 30.693 2.68 1.49700 81.54 5 73.339 Variable 6 -232.961 0.40
1.88300 40.76 7 9.734 4.14 8* -18.836 0.50 1.74156 49.21 9* 137.632
0.10 10 34.325 1.71 1.94595 17.98 11 -69.795 Variable 12 (stop)
.infin. 0.00 13* 9.782 3.00 1.74156 49.21 14* -123.245 0.10 15
12.882 2.24 1.59282 68.63 16 36.663 0.50 1.84666 23.78 17 7.155
1.75 18 18.641 1.96 1.58233 59.30 19* -23.188 Variable 20* 118.843
0.50 1.53071 55.69 21* 11.107 Variable 22* 80.000 1.69 1.53071
55.69 23* -16.169 Variable 24 .infin. 0.30 1.51633 64.14 25 .infin.
0.59 26 .infin. 0.50 1.51633 64.14 27 .infin. 0.53 Image plane
.infin. (Light receiving surface) Aspherical surface data 8th
surface K = 0.000 A4 = 3.46605e-05, A6 = -4.20407e-07 9th surface K
= 0.000 A4 = -3.63877e-06, A6 = -5.38516e-07 13th surface K = 0.000
A4 = -9.77271e-05, A6 = -3.43776e-07, A8 = -3.77130e-09 14th
surface K = 0.000 A4 = 7.41385e-05, A6 = -4.92054e-07, A8 =
6.96740e-09 19th surface K = 0.000 A4 = 2.32344e-06 20th surface K
= 0.000 A4 = -1.29535e-05 21th surface K = 0.000 A4 = 5.60767e-05
22th surface K = 0.000 A4 = -1.59700e-04, A6 = 1.49990e-06 23th
surface K = 0.000 A4 = -5.51926e-05, A6 = 1.57462e-06, A8 =
-1.18405e-08 Zoom data WE ST TE Focal length 6.10 18.56 62.92 Fno.
2.80 2.80 2.85 Angle of field 2.omega. 76.12 27.42 8.18 fb (in air)
8.07 5.69 4.36 Lens total length (in air) 68.02 70.48 79.74 d5 0.99
15.88 31.89 d11 27.98 11.23 2.28 d19 1.29 5.68 4.81 d21 2.63 4.96
9.34 d23 6.41 4.02 2.69 Unit focal length f1 = 54.84 f2 = -10.41 f3
= 12.83 f4 = -23.11 f5 = 25.48
Example 2
TABLE-US-00002 Unit mm Surface data Surface no. r d nd .nu.d 1
42.307 1.00 1.84666 23.78 2 30.737 4.28 1.49700 81.54 3 -401.369
0.18 4 26.342 2.83 1.49700 81.54 5 65.920 Variable 6 116.602 0.40
1.88300 40.76 7 8.895 3.15 8 -12.156 0.40 1.77250 49.60 9 36.438
0.25 10* 24.562 1.21 2.10300 18.05 11 -110.435 Variable 12 (stop)
.infin. 0.66 13* 11.124 3.08 1.72903 54.04 14* -32.464 0.12 15
18.451 1.81 1.51633 64.14 16 45.329 0.71 1.84666 23.78 17 9.344
1.14 18 21.264 3.34 1.49700 81.54 19 -11.666 Variable 20 -226.200
0.40 1.53071 55.60 21* 8.496 Variable 22 21.305 2.40 1.53071 55.60
23* -19.973 Variable 24 .infin. 0.30 1.51633 64.14 25 .infin. 0.40
26 .infin. 0.50 1.51633 64.14 27 .infin. 0.53 Image plane (Light
receiving surface) Aspherical surface data 10th surface K = 0.000
A4 = -1.13920e-05, A6 = -2.03573e-07 13th surface K = 0.000 A4 =
-8.31293e-05, A6 = 5.94132e-07 14th surface K = 0.000 A4 =
1.87727e-04, A6 = 2.01285e-07 21th surface K = 0.000 A4 =
1.93076e-05 23th surface K = 0.000 A4 = 3.46753e-05, A6 =
-1.57350e-06, A8 = 5.60450e-09 Zoom data WE ST TE Focal length 6.07
19.63 63.12 Fno. 2.83 2.84 2.84 Angle of field 2.omega. 77.37 25.82
8.08 fb (in air) 8.14 5.39 3.15 Lens total length 63.30 66.04 74.48
(in air) d5 1.00 13.85 26.11 d11 22.02 7.85 1.62 d19 1.24 6.79 7.84
d21 3.54 4.79 8.40 d23 6.66 3.90 1.66 Unit focal length f1 = 47.05
f2 = -8.00 f3 = 11.39 f4 = -15.42 f5 = 19.82
Example 3
TABLE-US-00003 Unit mm Surface data Surface no. r d nd .nu.d 1
38.959 0.83 1.92286 20.88 2 27.869 4.00 1.49700 81.61 3 -351.994
0.15 4 21.575 2.40 1.59282 68.63 5 71.413 Variable 6 -172.991 0.40
1.88300 40.76 7 9.158 3.20 8 -17.425 0.40 1.74330 49.33 9* 19.511
0.30 10 19.020 1.65 1.94595 17.98 11 -130.076 Variable 12 (stop)
.infin. 0.66 13* 10.945 2.58 1.74330 49.33 14* -36.192 0.10 15
10.654 1.70 1.51633 64.14 16 36.952 0.40 1.80810 22.76 17 7.957
1.70 18 64.297 1.96 1.49700 81.54 19 -11.420 Variable 20 200.000
0.40 1.51633 64.14 21 8.050 Variable 22 41.283 2.00 1.53071 55.60
23* -14.148 Variable 24 .infin. 0.30 1.51633 64.14 25 .infin. 0.40
26 .infin. 0.50 1.51633 64.14 27 .infin. 0.53 Image plane .infin.
(Light receiving surface) Aspherical surface data 9th surface K =
0.000 A4 = -3.95226e-05, A6 = 3.66462e-07 13th surface K = 0.000 A4
= -6.71053e-05, A6 = 4.99533e-07, A8 = -1.73747e-09 14th surface K
= 0.000 A4 = 1.98622e-04 23th surface K = 0.000 A4 = 3.86035e-04,
A6 = -3.40258e-07, A8 = -3.89880e-08 Zoom data WE ST TE Focal
length 5.04 16.25 52.41 Fno. 2.85 2.85 2.84 Angle of field 2.omega.
76.78 25.51 7.99 fb (in air) 5.64 4.18 2.73 Lens total length 63.21
60.35 61.26 (in air) d5 0.84 9.68 17.33 d11 26.87 10.97 1.35 d19
2.25 4.97 6.32 d21 2.79 5.73 8.71 d23 4.17 2.71 1.30 Unit focal
length f1 = 34.60 f2 = -7.81 f3 = 11.09 f4 = -16.26 f5 = 20.11
Example 4
TABLE-US-00004 Unit mm Surface data Surface no. r d nd .nu.d 1
28.506 0.80 1.84666 23.78 2 23.303 6.00 1.49700 81.54 3* -204.148
Variable 4 756.690 0.40 1.88300 40.76 5 10.501 4.50 6* -32.838 0.40
1.74320 49.34 7 28.837 0.10 8 20.002 2.10 1.94595 17.98 9 115.191
Variable 10 (stop) .infin. 0.80 11* 10.793 3.10 1.74320 49.34 12*
-116.505 0.15 13 11.023 1.75 1.51633 64.14 14 21.086 0.45 1.80810
22.76 15 7.460 1.60 16 14.808 2.80 1.49700 81.54 17 -17.892
Variable 18 -106.972 0.45 1.51633 64.14 19 6.455 Variable 20*
27.027 3.30 1.49700 81.54 21* -11.885 Variable 22 .infin. 0.30
1.51633 64.14 23 .infin. 0.40 24 .infin. 0.50 1.51633 64.14 25
.infin. 0.53 Image plane .infin. (Light receiving surface)
Aspherical surface data 3rd surface K = 0.000 A4 = 3.37875e-06, A6
= -1.49575e-09 6th surface K = 0.000 A4 = 1.24551e-05, A6 =
8.70362e-08 11th surface K = 0.000 A4 = -4.07065e-05 12th surface K
= 0.000 A4 = 1.24748e-04 20th surface K = 0.000 A4 = -1.46734e-04
21th surface K = 0.000 A4 = 8.52527e-05, A6 = -4.72599e-06 Zoom
data WE ST TE Focal length 5.23 18.12 62.92 Fno. 2.85 2.85 2.85
Angle of field 2.omega. 82.88 27.25 8.08 fb (in air) 5.97 4.76 2.03
Lens total length (in air) 76.95 73.14 79.43 d3 0.30 16.56 31.09 d9
37.01 12.75 1.65 d17 2.01 5.11 7.54 d19 2.96 5.25 8.42 d21 4.47
3.29 0.55 Unit focal length f1 = 58.31 f2 = -10.47 f3 = 11.94 f4 =
-11.77 f5 = 17.08
Example 5
TABLE-US-00005 Unit mm Surface data Surface no. r d nd .nu.d 1
42.309 1.00 1.84666 23.78 2 30.655 4.41 1.49700 81.54 3 -315.262
0.18 4 25.604 2.96 1.49700 81.54 5 63.431 Variable 6 204.249 0.40
1.88300 40.76 7 9.295 3.07 8 -13.077 0.40 1.77250 49.60 9 32.863
0.35 10* 23.126 1.21 2.10300 18.05 11 -218.634 Variable 12 (stop)
.infin. 0.66 13* 10.479 2.95 1.76802 49.24 14* -44.326 1.37 15
42.445 0.40 1.84666 23.78 16 9.322 0.84 17 15.027 3.64 1.49700
81.54 18 -12.418 Variable 19 47.678 0.40 1.53071 55.60 20* 9.948
Variable 21 39.823 2.18 1.53071 55.60 22* -19.956 Variable 23
.infin. 0.30 1.51633 64.14 24 .infin. 0.40 25 .infin. 0.50 1.51633
64.14 26 .infin. 0.53 Image plane .infin. (Light receiving surface)
Aspherical surface data 10th surface K = 0.000 A4 = -1.43277e-05,
A6 = -2.93628e-07 13th surface K = 0.000 A4 = -8.11392e-05, A6 =
4.69104e-07 14th surface K = 0.000 A4 = 1.73834e-04 20th surface K
= 0.000 A4 = 9.08553e-05 22th surface K = 0.000 A4 = 6.54949e-05,
A6 = -3.14591e-06, A8 = 4.77055e-08 Zoom data WE ST TE Focal length
6.07 19.53 63.12 Fno. 2.83 2.87 2.80 Angle of field 2.omega. 77.63
26.02 8.08 fb (in air) 7.64 5.13 3.05 Lens total length 62.79 66.56
73.63 (in air) d5 1.14 13.75 25.87 d11 21.95 8.33 1.62 d18 2.23
8.06 8.27 d20 3.43 4.89 8.42 d22 6.15 3.65 1.58 Unit focal length
f1 = 45.81 f2 = -8.09 f3 = 12.13 f4 = -23.77 f5 = 25.37
FIGS. 6A to 6L, 7A to 7L, 8A to 8L, 9A to 9L, and 10A to 10L
respectively show aberrations of the zoom lenses according to the
first to fifth examples in the state in which the zoom lenses are
focused on an object point at infinity.
FIGS. 6A to 6L are aberration diagrams of the zoom lens according
to the first example in the state in which the zoom lens is focused
on an object point at infinity. FIGS. 6A, 6B, 6C, and 6D
respectively show spherical aberration (SA), astigmatism (AS),
distortion (DT), and chromatic aberration of magnification (CC) at
the wide angle end. FIGS. 6E, 6F, 6G, and 6H respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens in the intermediate
focal length state. FIGS. 6I, 6J, 6K, and 6L respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens at the telephoto
end.
FIGS. 7A to 7L are aberration diagrams of the zoom lens according
to the second example in the state in which the zoom lens is
focused on an object point at infinity. FIGS. 7A, 7B, 7C, and 7D
respectively show spherical aberration, astigmatism, distortion,
and chromatic aberration of magnification of the zoom lens at the
wide angle end. FIGS. 7E, 7F, 7G, and 7H respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens in the intermediate
focal length state. FIGS. 7I, 7J, 7K, and 7L respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens at the telephoto
end.
FIGS. 8A to 8L are aberration diagrams of the zoom lens according
to the third example in the state in which the zoom lens is focused
on an object point at infinity. FIGS. 8A, 8B, 8C, and 8D
respectively show spherical aberration, astigmatism, distortion,
and chromatic aberration of magnification of the zoom lens at the
wide angle end. FIGS. 8E, 8F, 8G, and 8H respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens in the intermediate
focal length state. FIGS. 8I, 8J, 8K, and 8L respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens at the telephoto
end.
FIGS. 9A to 9L are aberration diagrams of the zoom lens according
to the fourth example in the state in which the zoom lens is
focused on an object point at infinity. FIGS. 9A, 9B, 9C, and 9D
respectively show spherical aberration, astigmatism, distortion,
and chromatic aberration of magnification of the zoom lens at the
wide angle end. FIGS. 9E, 9F, 9G, and 9H respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens in the intermediate
focal length state. FIGS. 9I, 9J, 9K, and 9L respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens at the telephoto
end.
FIGS. 10A to 10L are aberration diagrams of the zoom lens according
to the fifth example in the state in which the zoom lens is focused
on an object point at infinity. FIGS. 10A, 10B, 10C, and 10D
respectively show spherical aberration, astigmatism, distortion,
and chromatic aberration of magnification of the zoom lens at the
wide angle end. FIGS. 10E, 10F, 10G, and 10H respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens in the intermediate
focal length state. FIGS. 10I, 10J, 10K, and 10L respectively show
spherical aberration, astigmatism, distortion, and chromatic
aberration of magnification of the zoom lens at the telephoto end.
In aberration diagrams, .omega. represents the half angle of
view.
Next, parameter and values of conditional expressions in each
embodiments are described.
TABLE-US-00006 Ex- Ex- Ex- Ex- Ex- conditional ample ample ample
ample ample expression 1 2 3 4 5 (1) ft/fw 10.31 10.39 10.41 12.03
10.40 (2) Fno (T) 2.85 2.84 2.84 2.85 2.80 (3) .SIGMA.d/ft 0.43
0.42 0.46 0.44 0.41 (4) .DELTA.2G/|.DELTA.3G| 2.94 2.15 2.60 4.02
2.16 (5) .DELTA.2G/Lt 0.24 0.19 0.30 0.36 0.19 (6) |.DELTA.3G|/Lt
0.08 0.09 0.12 0.09 0.09 (7) (.beta.2T/(.beta.2w)/ 0.47 0.40 0.37
0.30 0.45 (ft/fw) (8) (.beta.3T/.beta.3w)/ 0.17 0.20 0.21 0.22 0.18
(ft/fw) (9) |f2|/ft 0.17 0.13 0.15 0.17 0.13 (10) f3/ft 0.20 0.18
0.21 0.19 0.19 (11) f5/ft 0.40 0.31 0.38 0.27 0.40
A flare stop may be provided in addition to the aperture stop in
order to eliminate unwanted light that may cause ghost images, lens
flare or the like. The flare stop may be disposed on the object
side of the first lens unit, between the first lens unit and the
second lens unit, between the second lens unit and the third lens
unit, between the third lens unit and the fourth lens unit, between
the fourth lens unit and the fifth lens unit, or between the fifth
lens unit and the image plane. A frame member may be adapted to cut
rays that may cause lens flare, or an additional part may be
provided for this purpose. Alternatively, a flare stop may be
provided on an optical component in the optical system by direct
printing or painting, or by attaching a sticker. The aperture of
the flare stop may have a circular, elliptical, rectangular,
polygonal, or other shape, or the shape of the aperture may be
defined by a curve expressed by a mathematical function. The flare
stop may be adapted to cut not only detrimental beams but also
beams that may cause coma flare etc. in the peripheral region of
the image.
Anti-reflection coating may be applied to each lens to reduce ghost
images and lens flare. It is desirable that the coating be
multi-layer coating, which can effectively reduce ghost images and
lens flare. Infrared cut coating may be applied to surfaces of
lenses and cover glasses.
Anti-reflection coating applied to the surfaces of lenses exposed
to air is widely used to prevent ghost images and lens flare. The
refractive indices of adhesives used on the cemented surfaces of
cemented lenses are significantly higher than the refractive index
of air. Consequently, the reflectivities of the cemented surfaces
areas low as or lower than surfaces having single-layer coating in
many cases. Therefore, anti-reflection coating is rarely applied to
the cemented surfaces of cemented lenses. However, anti-reflection
coating may be applied on the cemented surfaces. This will further
reduce ghost images and lens flare, and better images can be
obtained consequently.
Lens materials having high refractive indices are prevailing and
widely used in camera optical systems in recent times, because they
are advantageous in correcting aberrations. However, when a lens
material having a high refractive index is used in an element of a
cemented lens, reflection on the cemented surface cannot be
ignored. In such cases, it is particularly effective to apply
anti-reflecting coating on the cemented surface.
Effective use of coating on cemented surfaces is disclosed in, for
example, Japanese Patent Application Laid-Open No. 2-27301,
Japanese Patent Application Laid-Open No. 2001-324676, Japanese
Patent Application Laid-Open No. 2005-92115, and U.S. Pat. No.
7,116,482. The zoom lenses disclosed in these patent documents are
positive-lead type zoom lenses, and these documents describe
coating on cemented lens surfaces in the first lens unit. The
cemented lens surface in the first lens unit G1 having a positive
refractive power in the embodiment of the present invention may be
coated in a manner according to these documents. The coating
material may be selected appropriately based on the refractive
index of the base lens and the refractive index of the adhesive. A
coating material having a relatively high refractive power such as
Ta.sub.2O.sub.5, TiO.sub.2, Nb.sub.2O.sub.5, ZrO.sub.2, HfO.sub.2,
CeO.sub.2, SnO.sub.2, In.sub.2O.sub.3, ZnO, or Y.sub.2O.sub.3 or a
coating material having a relatively low refractive power such as
MgF.sub.2, SiO.sub.2 or Al.sub.2O.sub.3 may be chosen fitly, and
the coating film thickness may be set appropriately to meet the
phase condition.
Coating on the cemented surface may be multi-layer coating as with
coating on lens surfaces in contact with air. By using two or more
layers of coating materials in combination and selecting the film
thickness of each coating layer appropriately, the reflectance can
further be reduced and spectral characteristics and angular
characteristics of reflectance can be controlled.
It is effective to apply coating also to cemented surfaces in lens
units other than the first lens unit G1 for the same reason.
FIG. 11 is a cross-sectional view of a compact camera 1 as an image
pickup apparatus in which, the zoom lens according to the present
invention is used, and a small-size CCD (charge coupled device) or
a CMOS (complementary metal oxide semiconductor) is used. An image
pickup lens system 2 is disposed inside a lens barrel of the
compact camera 1, and an image pickup element surface 4 and a back
monitor 5 are disposed inside a camera body.
Here, it is also possible to let the image pickup lens system 2 to
be detachable from a single-lens mirrorless camera by providing a
mounting portion to the lens barrel. As the mounting portion, for
example, a screw type mount or a bayonet type mount could be
used.
The zoom lens described in the embodiments from the first
embodiment to the fifth embodiment is to be used as the image
pickup lens system 2 of the compact camera 1 having such
structure.
FIG. 12 and FIG. 13 show conceptual diagrams of a structure of the
image pickup apparatus according to the present invention in which,
the zoom lens has been incorporated in a photographic optical
system 41. FIG. 12 is a front perspective view showing an
appearance of a digital camera 40 as an image pickup apparatus, and
FIG. 13 is a rear perspective view showing an appearance of the
digital camera 40.
The digital camera 40 according to the embodiment includes the
photographic optical system 41 positioned on a capturing optical
path 42, a shutter button 45, and a liquid-crystal display monitor
47. When the shutter button 45 disposed on an upper portion of the
digital camera 40 is pressed, in conjunction with the pressing of
the shutter button 45, an image is captured through the
photographic optical system 41 such as the zoom lens according to
the first embodiment. An object image which has been formed by the
photographic optical system 41 is formed on an image pickup element
(photoelectric conversion surface) provided near an image forming
surface. The object image which has been received by the image
pickup element is displayed as an electronic image on the
liquid-crystal display monitor 47 provided on a rear surface of the
digital camera 40 by a processing unit. Moreover, it is possible to
record the electronic image which has been captured in a recording
unit.
(Internal Circuit Structure)
FIG. 14 is a block diagram showing an internal circuit of main
components of the digital camera 40. In the following description,
the processing unit mentioned above includes components such as
CDS/ADC section 24, a temporary storage memory section 17, and an
image processing section 18. A storage unit includes a storage
medium.
As shown in FIG. 14, the digital camera 40 includes an operating
section 12, a control section 13 which is connected to the
operating section 12, an imaging drive circuit 16 which is
connected to a control-signal output port of the control section 13
via buses 14 and 15, the temporary storage memory section 17, the
image processing section 18, a storage medium section 19, a display
section 20, and a set-information storage memory section 21.
The temporary storage memory section 17, the image processing
section 18, the storage medium section 19, the display section 20,
and the set-information storage memory section 21 are capable of
inputting and outputting data mutually via a bus 22. Moreover, a
CCD 49 and the CDS/ADC section 24 are connected to the imaging
drive circuit 16.
The operating section 12 includes various input buttons and
switches, and imparts event information input from outside (user of
camera) via the input buttons and switches to the control section
13. The control section 13 is a central arithmetic processing unit
such as a CPU with a built-in program memory which is not shown in
the diagram, and controls the overall digital camera 40 according
to a computer program which has been stored in the computer program
memory.
The CCD 49 is an image pickup element which is driven and
controlled by the imaging drive circuit 16, and which converts an
amount of light for each pixel of the object image which has been
formed through the image pickup optical system 41 to an electric
signal, and outputs to the CDS/ADC section 24.
The CDS/ADC section 24 is a circuit which amplifies the electric
signal input from the CCD 49, and also carries out
analog-to-digital conversion, and outputs image raw-data only for
the amplification and digital conversion carried out (bayer data,
hereinafter called as `RAW data`).
The temporary storage memory section 17 is a buffer such as a
SDRAM, and is a memory unit which temporarily stores the RAW data
output put from the CDS/ADC section 24. The image processing
section 18 is a circuit which reads the RAW data which has been
stored in the temporary storage memory section 17 or the RAW data
which has been stored in the storage medium section 19, and carries
out electrically, various image processing including a distortion
correction based on image-quality parameters which have been
specified by the control section 13.
The recording medium section 19 in which, a recording medium in the
form of a stick or a card with a flash memory is detachably
mounted, records and maintains the RAW data which is transferred
from the temporary storage memory section 17 and image data which
has been subjected to image processing in the image processing
section 18.
The display section 20 includes the liquid-crystal display monitor
47 and displays operation menu, image data, and RAW data captured.
The set-information storage memory section 21 is provided with a
ROM section in which various image-quality parameters are stored in
advance, and a RAM section which stores the image-quality
parameters which have been read from the ROM section by an input
and output operation of the operating section 12.
The digital camera 40 which is structured in such manner, by
adopting the zoom lens according to the present invention as the
photographic optical system 41, enables zooming, and enables
setting of a first mode which enables focusing including up to
infinity and a second mode in which it is possible to achieve
substantial (high) magnification, thereby making it possible to let
to be an image pickup apparatus which is advantageous for both
small-sizing and improved performance.
The zoom lens and the image pickup apparatus equipped with the same
according to the present invention are useful when high zoom ratio,
excellent optical performance, and small size are to be
achieved.
The present invention can provide a zoom lens that has a high zoom
ratio as high as or higher than 6 and excellent performance with
high speed throughout the focal length range from the wide angle
end to the telephoto end and well-corrected aberrations, while
being compact with small overall length (when in use and in the
collapsed state).
* * * * *